Modiki El Niños and Atlantic hurricane activity

It's an El Niño year, which typically means that Atlantic hurricane activity will be reduced. But not all El Niño events are created equal when it comes to their impact on Atlantic hurricane activity. Over the past 150 years, hurricane damage has averaged $800 million/year in El Niño years and double that during La Niña years. The abnormal warming of the equatorial Eastern Pacific ocean waters in most El Niño events creates an atmospheric circulation pattern that brings strong upper-level winds over the Atlantic, creating high wind shear conditions unfavorable for hurricanes. Yet some El Niño years, like 2004, don't fit this pattern. Residents of Florida and the Gulf Coast will not soon forget the four major hurricanes that pounded them in 2004--Ivan, Frances, Jeanne, and Charley. Overall, the 15 named storms, 9 hurricanes, and 6 intense hurricanes of the hyperactive hurricane season of 2004 killed over 3000 people--mostly in Haiti, thanks to Hurricane Jeanne--and did $40 billion in damage.

A new paper published in Science last Friday attempts to explain why some El Niño years see high Atlantic hurricane activity. "Impact of Shifting Patterns of Pacific Ocean Warming on North Atlantic Tropical Cyclones", by Georgia Tech researchers Hye-Mi Kim, Peter Webster, and Judith Curry, theorizes that Atlantic hurricane activity is sensitive to exactly where in the Pacific Ocean El Niño warming occurs. If the warming occurs primarily in the Eastern Pacific, near the coast of South America, the resulting atmospheric circulation pattern creates very high wind shear over the tropical Atlantic, resulting in fewer hurricanes. This pattern, called the Eastern Pacific Warming (EPW) pattern, occurred most recently during the El Niño years of 1997, 1987, and 1982 (Figure 1). In contrast, more warming occurred in the Central Pacific during the El Niño years of 2004, 2002, 1994, and 1991. The scientists showed that these Central Pacific Warming (CPW) years had lower wind shear over the Atlantic, and thus featured higher hurricane activity than is typical for an El Niño year. One of the paper's authors, Professor Peter J. Webster, said the variant Central Pacific Warming (CPW) El Niño pattern was discovered in the 1980s by Japanese and Korean researchers, who dubbed it modiki El Niño. Modiki is the Japanese word for "similar, but different".

Figure 1. Difference of Sea Surface Temperature (SST) from average during the peak of hurricane season, August-September-October, for seven years that had El Niño events (except for 2009, when the SST anomaly for July 1 - 3 is plotted). On the left side are years when the El Niño warming primarily occurred in the Eastern Pacific (EPW years). On the right are years when the warming primarily occurred in the Central Pacific (CPW years). Shown on the top of each plot is the number of named storms (NS), hurricanes (H), and intense hurricanes (IH) that occurred in the Atlantic each year. Atlantic hurricane activity tends to be more prevalent in CPW years than EPW years. An average hurricane season has 10 named storms, 6 hurricanes, and 2 intense hurricanes. Image credit: NOAA/ESRL.

What, then, can we expect the current developing El Niño event to do to 2009 hurricane activity? Kim et al. note that in recent decades, the incidence of modiki CPW El Niño years has been increasing, relative to EPW years. However, the preliminary pattern of SST anomalies in the Pacific observed so far in July (lower left image in Figure 1) shows an EPW pattern--more warming in the Eastern Pacific than the Central Pacific. If Kim et al.'s theory holds true, this EPW pattern should lead to an Atlantic hurricane season with activity lower than the average 10 named storms, 6 hurricanes, and 2 intense hurricanes. There is still a possibility that the observed warming pattern could shift to the Central Pacific during the peak portion of hurricane season, however. We are still in the early stages of this El Niño, and it is unclear how it will evolve.

Tropical Disturbance Summary (0600z 09JUL)=========================================An area of convection (90W) located at 6.2N 151.5E or 75 NM south southwest of Chuuk. Animated multispectral imagery shows improving convection associated with a developing wave in the easterlies and southerly low level clouds are under the convection hinting at a low level circulation center. The system is in an area of low vertical wind shear with good upper level outflow giving the system potential for convective organization.

Maximum sustained winds near the center is 10-15 knots with a minimum sea level pressure of 1007 MB. The potential for this disturbance to form into a significant tropical cyclone within the next 24 hours is UPGRADED TO FAIR.

We left for Ike too but I really think (just this one woman's intuition) that we don't have much to worry about this year. Probably. Maybe. A tiny chance. Teeny tiny possibility. 8-( ok. run for the hills, the hill country that is. LOL

Quoting TexasHurricane:Sorry, had a freaked out moment there.... Definitely something to keep in mind I guess and to check on later....

Hey its all good man... I didn't think you were freaking out.. it's just that the GFS which is usually a reliable model hasn't fared so well this year... next week at this time if it's still hinting at the possibility then we could start really pondering the situation.. good call though! :)

It looks like Anything could happen out in the Atlantic and Gulf of Mexico within the next two months with the current SST pattern out there in the Pacific.

One sign (locally for me) of this is that it's been abnormally hot the last two weeks and still going on here in coastal south Texas with very near 100 F temperatures close to the coast, constantly the last few days except for one and still quite high for that day.That is not normal here.

I'm not going to fall for a completely quiet 2009 tropical season with this. Even if only a few storms pop up late in the season, it doesn't mean at all they won't be significant or maybe even catastrophic.

Quoting sporteguy03:Ike,interesting run by GFS 00z right into the GOM on July 25th, 384 hours out. Speaking of Ike, looks like an Ike path maybe, but good entertainment though to watch late night. See you at 6z for another run of GFS.

the GFS is giving hints of something in the gulf around the 25th? For real? Just wondering because we had to evacuate for Ike...

Ike,interesting run by GFS 00z right into the GOM on July 25th, 384 hours out. Speaking of Ike, looks like an Ike path maybe, but good entertainment though to watch late night. See you at 6z for another run of GFS.

Tropical Disturbance Summary (0300z 09JUL)=========================================An area of convection (90W) located at 6.5N 151.0E or 100 NM southwest of Chuuk. Animated multispectral imagery shows improving convection associated with a wave in the easterlies and southerly low level clouds under the convection hinting at a low level circulation center. Additionally, Chuuk has observed winds out of the south for the last few hours with some 24 hour pressure falls. The system is also in an area of low vertical wind shear through good upper level outflow is lacking for now.

Maximum sustained winds near the center is 10-15 knots with a minimum sea level pressure of 1007 MB. The potential for this disturbance to form into a significant tropical cyclone within the next 24 hours is POOR.